Semiconductor wafers are typically fabricated with multiple copies of a desired integrated circuit design that will later be separated and made into individual integrated circuit chips. A common technique for forming the circuitry on a semiconductor is photolithography. Part of the photolithography process requires that a special camera focus on the wafer to project an image of the circuit on the wafer. The ability of the camera to focus on the surface of the wafer is often adversely affected by inconsistencies or unevenness in the wafer surface. The need for a precise image projection is accentuated with the current drive toward smaller, more complex integrated circuit designs. Semiconductor wafers are also commonly constructed in layers, where a portion of a circuit is etched on a first level and conductive vias are made to connect up to the next level of the circuit. After each layer of the circuit is etched on the wafer, an oxide layer is put down that allows the vias to pass through the oxide layer while covering the rest of the previous circuit level. Each layer of the circuit can create or add unevenness to the wafer as it is constructed. These imperfections are preferably smoothed out before generating the next circuit layer.
Chemical mechanical planarization (CMP) techniques are used to planarize the raw wafer and each layer of material added thereafter. Available CMP systems, commonly called wafer polishers, often use a rotating wafer holder that brings the wafer into contact with a polishing pad that is moving in the plane of the wafer surface to be planarized. A polishing fluid, such as a chemical polishing agent or slurry containing microabrasives, is applied to the polishing pad to polish the wafer. The wafer holder then presses the wafer against the rotating polishing pad and is rotated to polish and planarize the wafer.
The polishing pads commonly used in this process include belt-type pads and rotary-type pads. A belt-type pad typically consists of one or more sections of material that are formed into a belt by laminating or bonding the sections to each other and/or to a support structure. The joining of multiple sections of material requires the formation of joints where the sections meet. In a typical joint, there is a small space left between the two sections. These joints are subject to stresses that can cause the sections to delaminate. Delamination of the sections can result in a complete failure of the joint. The failure rate of the joints is increased as the slurry used with the pad seeps into the space between the sections.
A rotary-type pad typically consists of one or more sections of material that are joined together to form a pad. The pad is attached to a rotary machine that rotates the pad to polish a wafer. The joints in this type of pad are also formed by laminating or bonding the sections to each other and/or to a support structure and also subject to the same failure as the belt type pad. A polishing pad that overcomes these deficiencies is needed.